In manufacturing sporting goods, for example shoes or sports clothing, it is often necessary to permanently connect individual components together. Such components of sporting goods frequently comprise plastic materials. This must be taken into consideration when selecting a suitable method for connecting the components.
One option is to connect the components mechanically, for example by screwing or riveting the components. However, this may be disadvantageous, for example with respect to the look of the sporting goods, their weight or the durability or resilience of the connection.
A further possibility is to glue the components together. This option may have the disadvantage, for example, that gluing may require complex pretreatment of the components. It may, for example, be necessary, particularly in the case of plastic components, to first roughen and prime the surfaces of the components and to pre-dry the adhesive used for connecting the components in an oven. In addition, adhesives used for the gluing of plastic components are often harmful or environmentally hazardous.
In particular for connecting plastic components, various welding options have been used, for example using heat energy.
WO 99/56578 A1 relates to a machine for stretching shoe uppers and for attaching them to corresponding soles. US 2012/0272899 A1 relates to a system for applying hot melt adhesive powder onto a non-metallic object surface. DE 1 914 537 A relates to a method for gluing shoe shafts with soles with a heat-activatable glue. DE 698 11 251 T2 relates to a shock absorbing component and its manufacture.
U.S. Pat. No. 7,992,243 B2 relates to a custom fit system with adjustable last and a method for custom fitting athletic shoes. U.S. Pat. No. 5,522,954 relates to non-contact bonding of plastics. U.S. Pat. No. 9,027,623 B2 relates to a welding apparatus for conveyor belts and method. U.S. Pat. No. 8,747,584 B2 relates to a flashless welding method and apparatus. U.S. Pat. No. 8,302,649 B2 relates to an infrared welding device. EP 0 922 559 B1 relates to a process for joining components.
US 2007/0033750 A1 describes a system for custom fitting athletic shoes to a wearer. Shoes of a single width for each shoe length have at least a portion of the upper made of a heat malleable material to be custom fitted for the shoe width. The heat malleable material is subjected to infrared radiation until it becomes plastic and the width of the shoe may be adapted.
US 2014/0000043 A1 and US 2014/0000044 A1 describe methods for the manufacture of articles of footwear for which electromagnetic induction is used to heat up a last on which two or more shoe components are arranged and thus create a connection between the components.
WO 2012/099784 A2 describes a method for Through-Transmission Infrared Welding (TTIR) of plastic components. The surface areas of two plastic components, which are in contact during the welding, are treated before welding to increase the amount of laser energy absorbed in the connection area and thus to support the welding of the touching plastic components. A disadvantage of this method may be that one of the materials has to be transparent or semi-transparent to the laser light.
A common disadvantage of these methods is that the components which are being connected are already in contact when they are heated such that both components are heated up. This can result in a costly, time consuming and inefficient method. It can also be potentially damaging to one or both of the components due to the potentially different melting points of the materials involved (e.g. one material may already have degraded before the other is sufficiently heated). Moreover, in the methods known from the prior art, heat energy may be dissipated in regions of the components that are not involved in the creation of the connection between the components and this unwanted dissipation of heat energy can also be detrimental to the components.
It is therefore an objective underlying the present invention to provide improved methods and devices for the manufacture of sporting goods, for example shoes or sports clothing, which can account for the potentially different material properties of the different components and are fast, efficient and help to save energy. It should further be possible to largely dispense with the use of adhesives.